Turbine blades are exposed to high loads during operation. In particular, they have to withstand high temperatures in a chemically aggressive atmosphere. It is therefore necessary to cool them so as to prevent premature failure.
The inlet and outlet edges of turbine blades are subjected to particular load. In order to ensure effective cooling here, a multiplicity of cooling air bores are formed in the edges, which are mostly arranged in a row and through which cooling air is then blown out during operation.
Various methods and apparatuses for making cooling air bores in edges of turbine blades are known in the prior art. For example, DE 25 38 653 describes an electrolytic fine drilling method. In this method, a guide is placed onto the turbine blade and has a coaxial guide bore for each bore to be made. A tubular electrode is then pushed forward through each of the individual guide bores in the direction of the edge of the turbine blade in order to form the bores, the guide being intended to ensure that the tubular electrodes impinge onto the edge of the turbine blade at the desired location and at the correct angle.
It is likewise known from the prior art to make bores in the edges of a turbine blade by spark erosion with the aid of rotating electrodes.